A conventional lancing device generally has a basic structure in which a lancet holder holds a lancet in a housing to advance the lancet holder toward a tip end portion of the housing by resilient force generated by a predetermined operation of a spring. The forward movement of the lancet holder is performed with the tip end portion of the lancet holder pressed against the skin of the human body. The tip end portion of the lancet can be stuck into the skin of the human body to cause bleeding from the skin. The blood is taken as a sample for examination.
When a lancing device is used for sticking a lancet into the skin as described above, it is desirable for the lancet to be made adjustable in terms of the lancing depth into the skin for preventing the user from experiencing great pain or for avoiding excess or deficiency of the bleeding from the skin. Some of prior art lancets can be adjustable in the lancing depth into skin by the lancet (see JP-A-H11-9577 for example).
However, the prior art device has the following problems.
In recent years, the necessary amount of sample for precise analysis has been decreasing due to rapid improvement in performance of an analyzer used for sample analysis. This seems to be the trend for the future. The decrease in the necessary amount of sample analysis results in decrease in the bleeding amount by lancing. It follows that the lancet sticks just slightly into skin.
However, in the prior art, the adjustment rate of the lancing depth of the lancet is constant both in increasing and reducing the lancing depth of the lancet. Therefore, when the lancing depth of the lancet should be made small to cause slight bleeding from the skin, the lancing depth is adjusted with the same rate as in the case where the lancing depth of the lancet is large. Generally, when the lancing depth into the skin by the lancet is made relatively large, the increase in the bleeding amount is not precisely proportional to the increase in the lancing depth. On the other hand, when the lancing depth into the skin by the lancet is small, the lancing depth is relatively precisely proportional to the bleeding amount. In light of these, when a slight amount of bleeding is needed, it is desirable that the lancing depth of the lancet is adjusted more fine than in the case where a large amount of bleeding is needed. However, the above-described prior art device does not meet such requirements.